"It's the best—though I haven't done it," he said. "We have lots of lakes, too."

Farther down I-40, across the state line and looming at lunchtime, was the Texas city of Amarillo, near the center of the Panhandle. I stopped and had a steak, gassed the car again and set off into a different-looking desert, stonier, with clusters of junipers softening its appearance. Nearer Oklahoma, green turned to lush, and then to a great grassy expanse with browsing cattle and tall Texan bushy-boughed trees. Cattle and grassland, trees and meadows, from Shamrock all the way to the border and the even greener pastures of Oklahoma.

Wide-eyed, because it was my first look at the heartland, I saw Oklahoma as a ravishing pastoral, widely spaced towns proclaiming on enormous billboards their local heroes: Erick ("Home of Roger Miller, King of the Road"); Elk City ("Home of Miss America, 1981"). And at Yukon ("Home of Garth Brooks"), I could have hung a left and driven down Garth Brooks Boulevard.

I had always associated this part of America with dramatic weather—tornados, searing heat, thunderstorms. My expectations were met as dark pinnacles of storm clouds massed in the big sky ahead, creamy and marbled at their peaks and almost black below. This was not just a singular set of clouds but an entire storm front, visible in the distance and as wide as the plains—I could not see where it began or ended. The storm was formally configured, as a great iron-dark wall, as high as the sky, bulking over the whole of western Oklahoma, it seemed: the vertical clouds like darkening watchtowers.

This was fearsome and satisfying, especially the croaky weather warnings interrupting the music on the radio. I approached the towering storm and was soon engulfed by hail, wind and dark curtains of rain slashing across the flooded road. There was nowhere to stop, so I just slowed down, with everyone else. After an hour, I had passed through this wall of weather and was entering the dry, sunlit outskirts of Oklahoma City.

This relatively young city—it dates only from 1890—a tidy, welcoming place of broad streets, has a reputation for being God-fearing and hard-working ("Work Conquers All" is the state motto). Since 1995 the city has been known for one traumatic event, the bomb outrage by the murderer Timothy McVeigh, who had drifted here from Kingman, parking a rental truck full of explosives that leveled the Alfred P. Murrah Federal Building, killing 168 people, many of them women and children. The site was walking distance from my downtown hotel. Surrounded by trees, with some of the bomb-cracked walls still standing, the memorial is the most peaceful and spiritual place in the city.

"Everyone who was in the city has a memory of it," D. Craig Story, a local attorney, told me. "I was 50 blocks away in my office that morning. I had just picked up the phone to make a call. The big window of my office bowed in—didn't break but looked like it was going to turn into a bubble, the air pushing it. The sound of the blast came a few seconds later. Then the news of it."